1. Field of the Invention
The present invention relates to a gas detecting apparatus, a gas detecting method and a fuel cell vehicle equipped with the gas detecting apparatus.
Moreover, the present invention relates to a gas detecting apparatus equipped with at least two gas sensors each of which concentration outputting characteristic differ.
Priority is claimed on Japanese Patent Application No. 2004-191235, filed Jun. 29, 2004, Japanese-Patent-Application No. 2004-191236, filed Jun. 29, 2004, and Japanese Patent Application No. 2005-066184, filed Mar. 9, 2005, the content of which are incorporated herein by reference.
2. Description of Related Art
Hitherto, for example, in a fuel cell such as a conventional solid polymer membrane type fuel cell, a protecting apparatus having a hydrogen detector (gas sensor) disposed to a discharging system at an oxygen electrode side of the fuel cell is known well. This protecting apparatus cuts supply of fuel when the hydrogen detector (gas sensor) detects that the hydrogen at a fuel side leaks to the oxygen side through a solid polymer electrolyte membrane.
Moreover, as a gas sensor, for example, a gas catalytic combustion type gas sensor is known well. This gas catalytic combustion type gas sensor is equipped with a pair of a gas detecting element which is made from a catalyst such as a platinum and a temperature compensating element, and detects concentration of hydrogen, based on, for example, difference of electrical resistance between the gas detecting element and the temperature compensating element which is at a relatively low temperature such as an ambient temperature, when the gas detecting element becomes a relatively high temperature by heat which generates from combustion when hydrogen comes into contact with a catalyst such as platinum.
For example, the patent document 1 (Japanese Unexamined Patent Application, First Publication No. 2000-221152) has disclosed a technology of reducing power consumption, by turning on electricity intermittently to a heater-cum-an electrode which functions partly as a heater for heating the gas detecting element and partly as an electrode, as this kind of a gas sensor.
However, in the conventional technology, although it is effective for reducing the power consumption of the gas sensor itself, there is a problem of being hard to use it when it is installed into a system which has both an operating state and an idling state, for example, as a fuel cell vehicle, such that the gas detecting operation is kept in the idling state. That is, in the gas sensor of a catalytic combustion type, since the gas detecting element and the temperature compensating element are constituted as a pair of bridge circuits, a circuit which amplifies the output of the element is required, and hence power consumption will increase. Therefore, there is a problem of being hard to use it, because the power is dependent upon the electric power of the power unit which is installed in the system when the system is an idling state.
In particular, in a fuel cell vehicle which uses a fuel cell as a power source, since the battery of which capacity is restricted in the idling state of the vehicle must supply power to the gas sensor, the above-mentioned problem becomes still more significant.
Therefore, it is an object of the present invention to provide a gas detecting system and a fuel cell vehicle which can increase convenience and can perform detection of gas suitable for the state of the system, in a system which has both operating state and an idling state.
Next, in recent years, various sensors are proposed as a gas sensor which detects a detection target gas.
For example, the patent document 2 (Japanese Unexamined Patent Application, First Publication No. H08-75692) has disclosed a technology about a catalytic combustion type gas sensor which uses the combustion heat of the detection target gas (in this case, carbon monoxide gas).
Moreover, the patent document 3 (Japanese Patent No. 3146111) has disclosed a technology about a heat rays type semiconductor type gas sensor having low heat capacity which is equipped with an oxide semiconductor which mainly consists of tin oxide.
However, in the conventional technology, as a sensor to be installed in a system, a sensor of the same type is used. Therefore, detection accuracy will be limited by the peculiar concentration outputting characteristic of the sensor. Therefore, there is a problem that there is a possibility that sufficient detection accuracy cannot be acquired depending on the detection target region.
Therefore, it is another object of the present invention to provide a gas detecting apparatus which can detect concentration of the detection target gas with high accuracy corresponding to the detection target region.